The invention relates to an axial fan the housing of which, as viewed in the axial direction, has the external contour of a circle with uniformly circumferentially spaced identical radial projections, with a tubular part being arranged between the two axial boundary surfaces of the fan housing. A drive motor is mounted by means of spokes at one axial end of the housing. The drive motor drives a fan wheel which at least partly surrounds the drive motor. The blades of the fan wheel extend, within an annular flow channel defined between the drive motor and the tubular part, to about the other axial end of the tubular part of the fan housing. The tubular part, approximately midway between the axial ends thereof, has a circular interior cross-section which very closely surrounds the peripheral boundary contour of the fan wheel. At at least one axial end of the tubular part, the latter merges into the radial projections which are distributed uniformly about the circumference of the tubular part. In the region of those projections, the inner wall of the tubular part is set back from the peripheral boundary surface of the fan wheel interiorly of the external contour of the housing of the axial fan.
In particular, the invention is concerned with maximum utilization of the usually parallelepiped space defined by the external surfaces of the axial fan, in order to improve the performance of the fan, e.g., its air throughput. To this end, the projections or flared enlargements, particularly if these projections are located on the discharge side of the fan, make possible a considerable improvement in the performance of the fan, within the framework of the external contours in question.